Margins: Experimental Investigation of Hydrous Peridotite Melting beneath Volcanic Arcs

该项目的目标是(1)确定来自俯冲大洋岩石圈的富含H2O组分使地幔橄榄岩熔融而形成的含水部分熔体的组成特征和液线温度，以及(2)测量适合于模拟地幔楔形含水橄榄岩部分熔融过程中微量元素分馏的矿物/熔体分配系数。这些目标是通过实验确定(1)水合硅酸盐熔体的组成与二辉橄榄岩矿物组合在2.0至3.0 Gpa之间达到平衡，(2)向橄榄岩中添加不同数量的Na2O-K2O-H2O俯冲成分对部分熔融的影响，以及(3)在适合火山弧下地幔的条件下，不相容的微量元素在地幔矿物(单斜辉石、石榴石、角闪石)和水合部分熔体之间的分配。这项实验研究的结果将提供必要的岩石学和地球化学数据，以了解H2O在产生弧状岩浆中的作用，并确定与俯冲有关的岩浆过程从地幔转移到地壳的物质的组成。这些结果还将有助于提供一个框架，用于解释伊豆-博宁-马里亚纳和中美洲俯冲系统边缘重点地点的样品。

0112013GaetaniThe objectives of this project are (1) to determine the compositional characteristics and liquidus temperatures of hydrous partial melts formed through fluxing of mantle peridotite by a H2O-rich component from the subducted oceanic lithosphere, and (2) to measure mineral/melt partition coefficients appropriate for modeling trace element fractionations during partial melting of hydrous peridotite in the mantle wedge. These goals are being achieved by determining experimentally (1) the compositions of hydrous silicate melts in equilibrium with a lherzolite mineral assemblage at 2.0 to 3.0 GPa, (2) the effect on partial melting of adding variable amounts of a Na2O-K2O-H2O subduction component to the peridotite, and (3) the partitioning of incompatible trace elements between mantle minerals (clinopyroxene, garnet, amphibole) and hydrous partial melts at conditions appropriate for the mantle beneath volcanic arcs. The results from this experimental study will provide petrologic and geochemical data necessary for understanding the role of H2O in generating arc magmas and determining the composition of material transferred from the mantle to the crust by subduction-related magmatic processes. The results will also help to provide a framework for interpreting samples from MARGINS Focus Sites in the Izu-Bonin-Mariana and Central American subduction systems.